Pigment and method of making the same



The invention is offprimary utility Patented Aug. 27, 1935 UNITED Y STATES" PIGMENT AND .METHOD OF MAKING THE 7 Charles Park, Cuyahoga Falls, Ohio, assignor to The .Firestone Tire "& Rubber Akron, Ohio, a corporation of Ohio No Drawing, Application September 17," 19:32,- i

iSerialNo.633 ,687

iClaims. (01406-23),

when it is desired to produce a light-colored 7 rubber compound. Rubber compounded with the improved pigment has tear resisting characteristics at least equal to compounds using-channel gas black, and quite superior-to those using ordinary blanc fixe, zinc oxide, litharge, etc. as pigments.' r w I Thechief objects of'the invention are to pro vide a rubber composition havingtear resisting characteristics at least equal to compositions employing the best carbon black, without using the latter; to provideanovel pigment capable of im parting the aforesaid characteristics to vulcanized rubber; and to provide anovel method ofmaking a pigment of the above-mentioned character; -A further object is to provide sucha pigment. that may beeasily milled into a rubber-mix. Still another object is to provide'a novel composition of matterecomprising vulcanized rubber, compounded with such a'pigment. Other objects will be manifest. I The improved pigmentcomprises a mixture of ferric i. oxide- (F6203) andbarium sulphate (BaSOU and-"is prepared by reacting solutions of ferric sulphate (Fe2(SO4)3) and barium hydroxide (Ba(OI-I)-z); Theuseof bariumsulphate as a rubber pigmentis not new, but in its usual state is coarser grained than in the presentf'improved pigment, and does not impartto th'e rubber any superior tear or abrasion resisting qualities. It is known in the trade as blanc "fixe'and is usually prepared by reacting sodium-sulphate (NazSOr) or sodium acid sulphate (NaHSOr) and barium sulphide (BaS) or barium"- chloride (BaClz). Ferric oxide, made. by+a diiierent method than described herein, also has/ been used as a rubber pigment for coloring only, "but not with barium sulphate. The use of ferric oxide as a reinforcing agent heretoforev has been impractical because of its high cost. I Y In the manufacture of the improved'pigment on a small scale, asatura'ted solution offerric sulphate, approximately 830 grams anhydrous ferric sulphate to 1000 c. c. of wateris made up and filtered. A saturated solution of barium hy-' droxide is made up, filtered and decanted after standing a suitable interval. 'The saturated-some tion of barium hydroxide contains approximately as a sub- 33, grams of, anhydrousfbarium hydroxide per 1000 c. c. of water. To theierric sulphate solution is-added a determinate amount of-the -ba-' rium hydroxidesolution which is just: short of bringing the mixture to equivalency, themixture being constantly agitated" b ri hy;

1y aspossible Addit easosiiissaiom, aaamtsdhite). An im ortant feature-or thereaeuonis that all reactants are recovered'as insoluble solid precipitates, Anotherfeature of-the reaction is that no other reactionp'roduct is formed and there is no necessityfor washing the precipitate free from foreign materials. W i V V V The pigmentthus produced is-in the form of a very fine brown precipitate, thecrystal grains of I whichhave a tendency to grow rather rapidly is allowed to'settle, after which: it is decanted, and filtered. -.,If the. filter cake is now dried in an oven at 0. 111 the usual way the product is hard and' brittleta nd can be converted to usable form only with great difiiculty. To avoid this. diificulty the filtrate istreated, before drying, by agitatingwith'an' agent .such' as pine tar that induces excessive frothing the wholemixture becoming a foam of perhaps twice the original volume of the filtrate. In this form the filtrateis dried, the drying", being effected more rapidly than ifitwere ;not foamed, and'a finished product is produced that is soft and easily milled on the usual rubber-working mills. a

As a variant-of the process described, rubber latex is used as a protective agent. The latex is added'to the precipitate immediately after dec'ant'atio'n, the precipitate being recovered from the mixture by coagulating thev latex. The properties of theQp-igment thusproduced are similarto A B C D E 'f F G Stearicacid 3 3 4 4. Sulphur 3 3 '3" 3 3 3. 3 Zinc oxide 5 5 5 5 5 5 '5 NeozoneD l 1 1 1 I 1 l 1 Captax *2. .6 '.6 1.25 11.25 2.5 2.6. 2.5, Blane fire" 139.6 186.3 Carbon black" 56.2 75 Experimental pi gment. Smoked sheet- 100 100 v 100 100 Phenyl beta naphthylaminer Mercaptobenzothiazole.

the properties of pigment produced by the firstdescribed method.

The improved pigment is brown in color, and has a specific gravity of approximately 3.2. To

illustrate further the characteristics of the im- The stocks contain the following pigment loadlngsper volumes of rubber; A -30 volumes blancfixe' j B 40 volumes blanb flxe' C-30 volumes carbon black D-4 mes arb n bl ck- E- 30 volumes experimental pigment j F40 volumes experimental pigment;

G-47 volumesexperimentalpigment The stocks were vulcanized at a temperature of 260? F. and were tested for physical characteristics producing the following results:

. v $2 3 a Resista 0 ensi e ongaelongaat break tion persince to i tion, pounds cent lbs im- Pmm S 45 1150 300 60' 1225 3375 v 90' 1300 3100 V I 1325. 3075 D 15' 1075 2375 740 30 2700 3425 700 v 652 45 3100 3950 710 V 563 60' 3525 4050 720 323 90 3825 4125 650 120 1025 4100 590 F 30' B50 3050 V 45 950 3 3125 60' 950 3175 90' 1025. 3200 j 120' 950 2500 The foregoing data show fthatrubb erfcom-i pounded with carbonblack has higher tensile.

strength but lower tear resistance than rubber compounded ,with the improved pigment. A

peculiar feature of rubber compounded with the new pigment is that it rarely tears in a straight line but it shows extreme knottiness and a'tendency to tear in a reverse direction to the direction of pull. I I

In addition to the ingredients hereinbefore mentioned, it has been found that excellent results are obtainable where strontium hydroxide (Sr(OI-I)2, barium sulphide (BaS) or strontium sulphide (SrSY are substituted for barium hydroxide, and where ferrous sulphate (FeSO4) or aluminum sulphate (A1z(SO4) a) is substituted for ferric sulphate. The foregoing ingredients are mixed to produce reactions as follows:

In case it is desired to change the, ratio of barium sulphate (BaSOQ to ferric oxide (F8203) in the finished pigment, there may be addednto the mix at the time of precipitation sodium sul-r phatelNazSOQ, sulphuricacid (I-IzSO4) or acid sodium sulphate (NaHSO4)., An example is as follows: v v 1 4Ba(OH)2+Fe2 (S04) 3+Na2SO4= cresol, ortho cresoL'para cresol,. or: mixtures of the foregoing are examples of such additional agents. 1 I V V r r Other modifications may be resorted toywithout departing from the spirit of the invention or from, the scope of the appended claims.

.What is claimed is:

' 1; A pigment comprising a dried froth formed from ace-precipitated mixture of 1 barium sulphate and ferric oxide, with a foaming agent selected from the group consisting of pine tar, pine oil, cresylic acid, metal cresol, ortho cresol and para cresol. p 2. A composition of matter comprising rubber vulcanized in the presence of the reaction prodnets of a mixture, of the hydroxide of a metal from the group consisting of barium and strontium and the sulphate salt of a metal from the group consisting of iron and. aluminum: compounded. with the'rubber while in the form ,ofa dried froth.

3. A composition of matter comprising rubber vulcanized in the presence of the reaction prodnets of barium hydroxide and a sulphate salt of iron compoundedwith the rubber while in the form ofadried froth.

4. A composition of matter comprising rubber vulcanized in the presence of a co-precipitated mixture of ferric oxide and barium sulphate compounded with the rubber while in the form of a dried froth.

5. A composition of matter comprising rubber vulcanized in the presence of the reaction products of a mixture of the hydroxide of a metal from the group consisting of barium. and strontium and the sulphate salt of a metal from the group consisting of iron and aluminum compounded with the rubber while in the form of a dried froth.

6. A method of preparing vulcanized rubber compound which comprises mixing the hydroxide of a metal selected from the group consisting of barium and strontium with the sulphate salt of a metal selected from the group consisting of iron and aluminum, adding a protective colloid to the mixture, filtering out the precipitate, frothing the same to form a persistent froth, drying said froth to produce a light, porous cake, incorporat-' oxide, adding a protective colloid to the mixture,

filtering out the precipitate, frothing the same to form a persistent froth, drying said froth to pro-. duce a light, porous cake, incorporating said cake in a rubber batch including sulphur, and vulcanl5 izing the resulting compound.

CHARLES R. PARK. 

